1. Field of the Invention
The invention generally relates to receivers in data communication systems, and in particular to receivers and operation methods having an average tracking mechanism.
2. Description of the Related Art
A wireless local area network is a flexible data communications system implemented as an extension to or as an alternative for, a wired LAN. Using radio frequency or infrared technology, WLAN (Wireless Local Area Network) systems transmit and receive data over the air, minimizing the need for wired connections. Thus, WLAN systems combine data connectivity with user mobility.
Today, most WLAN systems use spread spectrum technology, a wide-band radio frequency technique developed for use in reliable and secure communication systems. The spread spectrum technology is designed to trade-off bandwidth efficiency for reliability, integrity and security. Two types of spread spectrum radio systems are frequently used: frequency hopping and direct sequence systems.
The standard defining and governing wireless local area networks that operate in the 2.4 GHz spectrum, is the IEEE 802.11 standard. To allow higher data rate transmissions, the standard was extended to 802.11b that allows data rates of 5.5 and 11 Mbps in the 2.4 GHz spectrum. This extension is backwards compatible.
When operating a WLAN receiver or a receiver in another data communications system, code synchronization is necessary because the code is the key to despreading the desired information. Generally, a good synchronization is achieved when the coded signal arriving at the receiver is accurately timed in both its code pattern position and its rate of chip generation.
Referring now to FIG. 1, a block diagram of a conventional WLAN receiver 100 is shown. Via one or more antennae 110 the receiver receives a data stream from a WLAN transmitter and feeds the antenna output to a signal pre-processing unit 120. The received data signals are pre-processed in the signal pre-processing unit 120 and then handed over to the synchronization unit 130. After synchronizing the received data signals the synchronized data signals are handed over to the digital signal processing unit 140 for further digital signal processing.
When synchronizing received data signals as well as when performing other pre-processing or processing operations in data communication receivers, it might be necessary to have a smoothing mechanism that averages the amplitudes of incoming data samples and keeps track of this running average. For calculating the average value, conventional receivers need to buffer a number of most recently received samples and have to continuously update the buffer contents. In particular if several average values have to be calculated separately which all relate to the incoming data stream, and further if the data samples are complex data samples, a significantly high number of buffer registers are required, leading to a high die area occupation. This reduces the overall efficiency and increases the circuit development and manufacturing costs.